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Typed Utilities ​

Use the is namespace for runtime checks with TypeScript narrowing.

ts
import { is } from '@vielzeug/toolkit';

Available Methods ​

  • is.array
  • is.boolean
  • is.date
  • is.defined
  • is.empty
  • is.equal
  • is.fn
  • is.greaterThan
  • is.greaterThanOrEqual
  • is.lessThan
  • is.lessThanOrEqual
  • is.match
  • is.nil
  • is.number
  • is.object
  • is.primitive
  • is.promise
  • is.regex
  • is.string
  • is.typeOf
  • is.within

Standalone numeric predicates:

  • isGreaterThan
  • isGreaterThanOrEqual
  • isLessThan
  • isLessThanOrEqual
  • isWithin

Example ​

ts
import {
  is,
  isGreaterThan,
  isGreaterThanOrEqual,
  isLessThan,
  isLessThanOrEqual,
  isNumber,
  isWithin,
} from '@vielzeug/toolkit';

function normalize(value: unknown) {
  if (is.string(value)) return value.trim();
  if (is.number(value)) return value.toFixed(2);
  if (is.array(value)) return value.length;
  if (is.nil(value)) return null;
  return value;
}

const ok = is.equal({ a: 1 }, { a: 1 });
const match = is.match({ a: 1, b: 2 }, { a: 1 });
const tag = is.typeOf(new Date()); // 'date'

const predicates = {
  isNumber: isNumber(4),
  isWithin: isWithin(5, 1, 10),
  isGt: isGreaterThan(5, 4),
  isGe: isGreaterThanOrEqual(5, 5),
  isLt: isLessThan(4, 5),
  isLe: isLessThanOrEqual(5, 5),
};

console.log(normalize('  hi  '), ok, match, tag, predicates);

Standalone Predicate Pages ​